1. Field of the Invention
The field of this invention is enteric coatings for orally ingestible substrates such as pharmaceutical tablets and dietary supplements.
2. Description of the Prior Art
Within this field, there are already a number of enteric coating formulations that are useful, including Acryl-EZE® and Sureteric®, both manufactured and sold by the Assignee of present application. However, all of the components of currently marketed enteric coating formulations are not approved for use in food, nutritional supplements and pharmaceutical applications in every target market in the world. Furthermore, there is a continuing need in the food, nutritional supplements and pharmaceutical markets to develop novel, enteric-coated products that may allow pharmaceutical or nutritional supplements companies to positively differentiate themselves from competition.
A technical brochure entitled “Alginates for Pharmaceutical Applications”(Code: PHARM/ALG/0800), published by International Specialty Products, the disclosure of which is incorporated herein by reference, indicates that alginates such as sodium alginate have been used in some commercial tablet coating systems to achieve an enteric barrier in the stomach. It is further indicated that alginates are dissolved in water at the 5-10% level and that films with greater integrity are produced if a plasticizer, such as glycerine or propylene glycol, is incorporated. There is no disclosure or suggestion in the brochure, however, concerning how coating at a solids level greater than 10% in water, which would result in a faster coating process and an overall more economical operation, could be carried out. Furthermore, increasing the concentration of sodium alginate in water above 10% (w/w) will result in a solution viscosity that will make pumping and spraying the solution difficult or impossible.
U.S. Pat. No. 6,365,148 describes multiple systems capable of achieving an enteric effect when coated onto lactic acid bacteria granules. It is disclosed that a sodium alginate coating alone at a low temperature or in combination with a “controlled release” topcoat, which may be comprised of sodium alginate and/or ethylcellulose, may be used to impart an enteric effect. Nowhere is it stated that the controlled release (top coat) layer alone, nor the specific combination of ethylcellulose and sodium alginate by themselves in a single coating layer, could function as an effective enteric coating. Furthermore, the '148 patent discloses the use of a limited list of plasticizers that are not necessarily the most preferred for film-forming and organoleptic properties. For example, the '148 patent is silent regarding the use of dibutyl sebacate and medium chain triglycerides (also known as fractionated coconut oil).
In spite of the improvements provided in the art, there continues to be a need for improved enteric coating systems. The present invention addresses this need.